The invention relates to an eccentric press for molding simple workpieces, for example, balls or the like objects, from rod or strip offcuts or the like, in each of two press molds arranged one on either side of a feed device and having a reciprocating die and a stationary die fixed in the press frame, wherein the workpieces to be molded are cut off by a shearing knife reciprocatable transversely to the direction of advancement of the workpiece stock and are delivered alternately to one of the two press mods by a feed device driven in synchronism with the shearing knife.
In heretofore known conventional eccentric presses of this type a pressing operation would take place at each full revolution of the eccentric shaft, and this generally takes place in the forward movement of the slide carrying the movable die. The exceptionally high forces which come into action in this operation demand a correspondingly great degree of stability of the bed of the press supporting the stationary die. The output of such a press depends solely upon the speed with which one working cycle is completed, that is to say one opening and closing operation of the two dies as well as the feeding of the working material. However, an increase in the working speed is in practice only achievable at the expense of the masses being moved to the reduction of which narrow limits are set. For the purpose of increasing the output of such eccentric presses while at the same time achieving an economic utilization of the structural possibilities of a simple press it has already been proposed to arrange at each side of a feed device a respective press mold whose movable dies are driven by the eccentric shaft having crank portions staggered through 180.degree.. Between the two stationary dies there is mounted a reciprocatable shearing knife, which is provided at both of its end faces with a cutter and a workpiece recetacle for alternate feeding to a respective one of the two dies, such as disclosed in U.S. Patent applicaton Ser. No. 545,062 filed Jan. 29, 1975, now U.S. Pat. No. 3,972,216.
The present invention is based upon such an improved eccentic press and takes as its purpose the improvement and simplification of the functional cycle of such apparatus, particularly for the purpose of achieving a higher output.
For this purpose according to the present invention the shearing knife is arranged at the workpiece entry side, and the feed device is arranged at the ejection side of a stationary shearing bushing guiding the rod stock forming the workpiece, while the feed device is mounted for movement in synchronism with the press working cycle between the ejection side of the shearing bushing and alternate ones of the two press molds in such a manner that the feed device simultaneously receives a workpiece at the ejection side of the shearing bushing while it is delivering another workpiece at one of the press molds.
The separation of the shearing function from the feeding function is the condition for the employment of a shearing knife which performs only a small reciprocating movement with respect to a fixed shearing anvil acting as an opposing cutting edge behind the shearing knife in the direction of motion. After the ejection from the shearing anvil of the previously cut off workpiece, the latter is gripped by the feed device which assumes a purely transporting function to deliver the workpiece alternately to one of the two press molds. The fact that each function of the apparatus is allocated to an individual member makes it possible to simplify the structure of the press and to increase its efficiency.
According to a further feature of the invention the shearing knife is in the form of an annular knife guiding the rod of working material, the stroke of this knife being smaller than the diameter of the rod. Experience has shown that the stroke needs only be one-third of the thickness of the workpiece which is to be separated, that is to say one-third of the diameter of the width of the workpiece rod. This depth of cut is completely adequate for the parting operation because the remainder of the cross section of the workpiece breaks away. The separated workpiece is first of all fed into the shearing anvil and is only ejected upon displacement of the supply of material.
It falls within the scope of the invention to arrange at a suitable distance from the ejection aperture of the shearing anvil a stop, preferably an adjustable stop, for limiting the feed of the workpiece material.
By the adoption of this simple procedure in combination with a selection of the profiles of working material which are available it is possible to design the dimensions of the blanks of raw material necessary for producing various balls.
More particularly in a further embodiment of the invention taking a particularly advantageous practical form, the feed device includes at least two sets of gripper jaws which are arranged to be movable between the ejection side of the shearing bushing and a respective one of the press molds, such movement taking place in at least an arcuate path about an axis directed substantially parallel to the axis of the shearing bushing. In any case preferably the drive for the feed device is derived from the press drive itself in order to maintain the necessary synchronisation of the various movements. While one set of grippers is situated before the ejection opening of the shearing bushing for the purpose of accepting at that position a workpiece blank cut off in a previous working cycle, another set of grippers is feeding a similar workpiece blank between the two dies of the press mold. The condition of the feed device is therefore that it is either in the course of making its reciprocating movement or else is in a temporary state of rest prior to making such movement. With each new movement of the feed device, the one set of grippers travels from the shearing bushing to the other press mold while the other set of grippers arrives in front of the ejection opening of the shearing bushing. This working cycle is continuously repeated.
In a particular practical form of the invention the feed device includes a double armed pivoted lever carrying upon each arm a set of grippers, whereby each arm reciprocates between the ejection side of the shearing bushing and a respective press mold. This motion can be derived, for example, from a crank drive. In this practictical example the press molds and the shearing bushing are situated upon a common arc whose radius corresponds to that form the opening in the grippers to the pivot axis of the feed device.
A further practical form of the invention makes use of a feed device having two synchronously driven pivoting arms each of which has a set of grippers at each end thereof, these pivoting arms rotating about parallel pivoting axes and being angularly staggered with respect to each other, and the arcuate paths of the pivoting arms touching each other at a contact point at which is situated the ejection opening of the shearing bushing, while a press mold is arranged upon each individual arcuate path. Advantageously the two pivoting arms have a Maltese cross drive. This operates directly upon the one pivoting arm, which in turn is in driving connection with the other pivoting arm through a chain drive or the like.
The invention provides a further alternative arrangement, wherein the feed device has two sets of grippers and is mounted for reciprocating movement along a linear path between the two press molds and the intervening shearing bushing in which case the spacing distance of a respective press mold from the shearing bushing, corresponds to that between the two sets of grippers. Each of the various design possibilities for the feed device contributes, together with the provision of the shearing knife in accordance with the invention, to the result that the function of cutting the workpiece blank is separated from the function of conveying the cut workpiece to the respective press mold which fact alone achieves an increase in output representing a multiple of that produced by conventional ball presses.
Other features which are considered characteristic of the invention are set forth in the appended claims.
Although the invention is illustrated and described in relationship to specific embodiments, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.